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Bithalamic T2 hypointensity: A diagnostic clue for Sandhoff ’s disease Devendra Kumar, Subramaniyan Ramanathan, Maneesh Khanna, Yegu Palaniappan 1

Department of Radiology, Hamad Medical Corporation, Doha, Qatar

A 6‑month male child with uneventful perinatal history presented with developmental delay, poor visual contact and psychomotor regression. On neurological examination, he was hypertonic with brisk deep tendon reflexes and exaggerated startle reflex. Fundoscopic examination revealed cherry‑red spot in both the eyes. There was family history of neurometabolic disease in a cousin. Magnetic resonance imaging (MRI) brain demonstrated bilateral symmetrical T2 hypointensity and T1 hyperintensity involving the thalamus. Bilateral basal ganglia appeared swollen with subtle T2 hyperintensity of putamen. Bilateral cerebral white matter showed diffuse symmetric T2 hyperintensity suggesting delayed myelination [Figures 1 and 2]. Corpus callosum was thinned out [Figure 3]. No significant cortical atrophy, brainstem or cerebellar abnormalities identified. Enzymatic assay revealed deficiency of both hexosaminidases A and B confirming the diagnosis of Sandhoff’s disease. Sandhoff’s disease is a rare lysosomal storage disorder caused by a deficiency of both hexosaminidases A and B resulting in accumulation of GM2 ganglioside in the brain. Three different forms of Sandhoff’s disease have been described: Classic infantile, juvenile and adult late onset. Classic infantile form is the most common and severe form, presenting between 3 and 9 months of age as in our case. Clinical features include muscular hypotonia or hypertonia, tonico‑clonic or myoclonic seizures, visual deficit, and psychomotor retardation. [1] Computed tomography (CT) brain features include bilateral symmetric thalamic hyperdensity with non‑specific bilateral white matter hypodensity. MRI is the imaging modality of choice and shows characteristic bilateral thalamic

T2 hypointensity and putaminal T2 hyperintensity. Thalamic hypointensity has been attributed to accumulation of GM2 ganglioside and possibly calcium. [2] Other features include diffuse cerebral white matter T2 hyperintensity due to delayed and hypomyelination, eventually leading to diffuse cerebral atrophy and rarely brain stem and cerebellar abnormalities. Bilateral thalamic T2 hypointensity is considered a sign of lysosomal storage diseases and can be seen in GM2 gangliosidosis  (Tay‑sach’s and Sandhoff’s diseases), Neuronal ceroid lipofuscinosis (NCL) and Krabbe’s disease. [3] Tay‑sach’s and Sandhoff’s diseases can be distinguished clinically by presence of hepatosplenomegaly in Sandhoff’s disease and confirmed by enzyme assays. NCL shows similar features but with early and severe cerebral atrophy. In Krabbe’s disease T2 hypointensity is more extensive involving the basal ganglia, central white matter and cerebellum in addition to thalamus.[1] Presence of bithalamic T2 hypointensity is a characteristic feature of lysosomal storage disease and helps in performing limited specific investigations for diagnosis of inherited neurometabolic disorders.

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Neurology India | Jul-Aug 2014 | Vol 62 | Issue 4

Figure 1: Axial T2 weighted MRI reveals bilateral symmetric thalamic hypointensity and subtle hyperintensity of swollen putamina. Also diffuse white matter hyperintensity seen indicating delayed myelination

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Figure 2: Axial T1 weighted MRI shows bilateral symmetric thalamic hyperintensity and subtle hypointensity of putamina

Address for correspondence: Dr. Subramaniyan Ramanathan, Al‑Wakra Hospital, Hamad Medical Corporation, PO BOX: 82228, Doha, Qatar. E‑mail: [email protected]

References 1.

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Saouab R, Mahi M, Abilkacem R, Boumdin H, Chaouir S, Agader O, et al. A case report of Sandhoff disease. Clin Neuroradiol 2011;21:83‑5.

Figure 3: Sagittal T1 weighted MRI shows diffuse thinning of corpus callosum. No cerebral or cerebellar atrophy

2.

Hittmair K, Wimberger D, Bernert G, Mallek R, Schindler EG. MRI in a case of Sandhoff’s disease. Neuroradiology 1996;38:S178‑80. 3. Autti T, Joensuu R, Aberg L. Decreased T2 signal in the thalami may be a sign of lysosomal storage disease. Neuroradiology 2007;49:571‑8. How to cite this article: Kumar D, Ramanathan S, Khanna M, Palaniappan Y. Bithalamic T2 hypointensity: A diagnostic clue for Sandhoff's disease. Neurol India 2014;62:475-6. Source of Support: Nill, Conflict of Interest: None declared.

Neurology India | Jul-Aug 2014 | Vol 62 | Issue 4

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Bithalamic T2 hypointensity: a diagnostic clue for Sandhoff's disease.

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